rs-0.6.0 — Rust interpreter and packages#

Marslang is now an interpreted language. The JavaScript backend is removed: marslang file.mars parses, checks, and runs a program directly in Rust. Node is no longer needed to run programs or tests.

Interpreter#

• src/interp.rs is a tree-walking interpreter over the resolved syntax tree; src/value.rs holds runtime values. The previous runtime.js.inc semantics are preserved: numeric kinds, checked integers, fixed containers, deep copies, grapheme-based strings, slicing, and the error kinds.
• CLI: marslang file.mars or marslang run file.mars runs a program; marslang check file.mars reports compile errors without running; marslang --version. The compile ... -o out.js command is removed.
• Runtime errors print error: <Kind>: <message> and exit with status 1.
• Calls nested deeper than 10,000 levels raise RangeError: maximum call depth exceeded.
• The REPL shows only the output produced by each new line and discards lines that fail to compile or run.
• String segmentation uses the unicode-segmentation crate.

Behavior changes from rs-0.5.0:

• Numbers compare by exact value across every kind: 1 == longint(1) and longint(5) < 10 are true, and equal numbers share set elements and map keys.
• Calling a function, method, or built-in with the wrong number of arguments raises TypeError; reading a missing family field raises TypeError.
• A block function without ret returns null.
• Containers print readably, such as [1, 2], {"k": 1}, and Box { v: 3 }. The display format is still not a stable serialization format.
• Integer overflow of 32-bit operands reports int overflow.

Packages#

takepkg is a package system, similar to Python's:

• takepkg std.math; loads a standard package built into marslang.
• takepkg util; loads util/init.mars (a package directory) or util.mars from the main program's directory; takepkg shapes.circle; maps to subdirectories.
• takepkg .sibling; and takepkg ..parent; are relative imports inside packages.
• Importing a.b runs a/init.mars first. Each package loads once. Packages export functions, families, and fixed/hot bindings; names starting with _ are private. Circular imports are rejected.

See Packages.

Standard library in Marslang#

std.math (42 functions, six constants) is written entirely in Marslang in std/math.mars, including argument checks, rounding, signs, integer pow, hypot, and interpolation. Only irreducible primitives are native Rust packages under std/rs/: rs.core (raise a named error, read a value's kind) and rs.math (platform float functions). Only standard packages may import rs.*.

build.rs registers every std/*.mars file as std.NAME and every std/rs/*.rs file as rs.NAME, so adding a standard package needs no list edits.

Validation#

cargo test passes 78 tests (9 unit, 69 execution, none ignored) on Windows Rust and on WSL-native Rust. Execution tests run programs in the interpreter and assert their output or runtime errors.

Remaining work#

A per-user package directory (such as C:\Users\<user>\marslang_pkgs) and an installer are planned. Wildcard imports, decorators, deque, further standard packages, match, run/handle/then, async, and self-hosting remain pending.